Ultrasonic measurement is a vital non-destructive tool used to explore the characteristics of the perovskite manganite materials. La1-xCaxMnO3 perovskite samples with the composition of x= 0.70 and 0.75 were prepared using the solid state reaction technique. The crystalline nature of the samples was confirmed by the XRD patterns. The samples were found to have orthorhombic structure with no secondary phases. The relative variation in longitudinal velocity and its attenuation was measured out in the temperature range from 500 to 700 K using the through transmission method at the fundamental frequency of 5 MHz. The temperaturedependent observations showed anomalous behaviour at the transition temperatures. The anomalies observed at the temperatures 640 and 560 K for the samples for the composition x=0.70 and 0.75 were used to explain the high temperature metal-insulator transition existing in the prepared samples. Further, the investigation reveals that the magnetic entropy increases with a decrease in the doping concentration of calcium in the samples.
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In-situ ultrasonic measurements on La0.7Sr0.3Mn1-xNixO3 perovskite manganite material (x = 0.0 and 0.02) have been carried out on the samples synthesized by solid state reaction technique. The X-ray diffraction patterns show that the samples have single phase rhombohedral structure. The temperature dependent ultrasonic longitudinal and shear velocity measurement on the samples was used to reveal the phase transition temperature i.e., Ferro to Para magnetic phase transition temperature (TC).The ultrasonic measurementsalso confirm that the Ni doping in La0.7Sr0.3Mn1-xNixO3 perovskites lead to a decrease in TC. The replacement of Mn4+ ions by Ni2+ ions caused the change in the structural parameters, the constitution of Mn3+ and Mn4+ ions and makes the AFM phase stronger in the samples.
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